The goal of this research is to investigate the possibility of relationships existing between intracellular levels of the enzymes adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) and the functional properties of certain human lymphocyte subpopulations. ADA and PNP were chosen for study because of the known association between their absence and severe form of human immunodeficiency. Combinations of rosette depletion and density gradient techniques will be used to isolate subpopulations. T-suppressor cell subpopulations are of major interest, and studies will be designed to characterize them by their ability to influence DNA and immunoglobulin synthesis in vitro. In concurrent studies, attempts will be made to serially measure the enzyme levels in isolated subpopulations during mitogenic stimulation. Additionally, subpopulations obtained from well characterized immunodeficient patients will be studied for possible correlations between disordered function and altered ADA and PNP levels.